Another holiday weekend, another Dumbarton Bridge closure.

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Drivers will likely experience longer travel times this Labor Day weekend as the Dumbarton Bridge closes for construction work.

Both directions of the bridge, which runs 1.6 miles and connects Alameda and San Mateo counties, will be closed from 10 p.m. Friday to 5 a.m. Tuesday to bring the bridge up to seismic code, Dumbarton Bridge Seismic Safety Project spokeswoman Effie Milionis Verducci said.

The Metropolitan Transportation Commission is urging motorists to carpool or use public transit this weekend with longer-than-usual traffic delays expected near the Interstate Highway 880 and U.S. Highway 101 corridors of the bridge, commission spokesman John Goodwin said.

Drivers electing to use their own vehicles should opt for alternate routes, Goodwin said.

Drivers in the South Bay can use state Highway 237, and those further north can use state Highway 92 over the San Mateo Bridge to connect Highway 101 with I-880, he said.

Goodwin said drivers can call 511 and select "Traffic" in the main menu to get up-to-date traffic conditions and alternate routes to take. Drivers can also check 511.org for traffic updates, he said.

During the closure, construction crews will be replacing the seismic joints on the eastern side on the main deck of the bridge with a larger joint, Verducci said.

The new joint will raise the deck five inches and allow it to move 42 inches -- 22 inches more than the old joint allowed -- in the event of a seismic event, she said.

The project has been ongoing since the summer of 2010 and will be 90 percent complete after this weekend's project, Verducci said.

Both touchdown spots, in Newark and Menlo Park, as well as the footing in the water, have been reinforced with concrete and rebar, she said.

Over the Memorial Day weekend, the entire bridge was closed to retrofit the main deck on the west end of the bridge and put a new joint, allowing the deck to move 42 inches in a seismic event, Verducci said.

Traffic over the Memorial Day weekend was "reasonably smooth," Goodwin said, and he said the commission expects much of the same traffic flow over the Labor Day weekend.

"The expectation is that it will create some delays, but not major delays," Goodwin said.

Upon completion of the project, expected in early 2013, the Dumbarton Bridge will be state of the art, Verducci said. The retrofit will increase the bridge's flexibility and stability in the event of a major earthquake, she said.

The closure over the weekend will be the last full closure of the Dumbarton Bridge during the project, Verducci said.

As crews complete the project, there will be nightly closures to one or two lanes in either direction, but they shouldn't affect traffic flow, she said.

The Bay Bridge is the last state-owned toll bridge in the Bay Area that requires a seismic retrofit, Verducci said. That ongoing project is expected to be complete some time next year, she said.